Heretofore, there have been different types and methods used for fabricating propellers. These methods include pattern machining using numerical control equipment and forging or a combination of these techniques. The methods requiring post machining for finishing and polishing the propeller greatly add to fabrication expense. In order to keep expenses at a minimum some economies are necessary. For example, the twist angle of the hub to the tip of the blade is not consistent in current propellers because of stress relief occuring during the machining process. This occurs primarily in metal propellers but also occurs to a more limited extent to composite wooden propellers. In addition, limitations of current machining requires non-optimal transition from the hub of the propeller to the blade. This comprises smooth air flow which reduces propeller efficiency. Propellers in current use are fabricated using compromises between what is required from an aerodynamic point of view and what can be fabricated from a practical cost point of view. In designing a producible propeller, by necessity, fabrication costs as related to functional value is a primary consideration.
The use of injection molding techniques permits, for the first time, primary consideration to be given to the aerodynamic requirements of the design of the propeller with no requirement to conform to conventional fabrication technique limitations. The injection molding manufacturing approach with materials which have not previously been used for prepellers has produced a highly efficient propeller at a low cost. A comparable two-bladed wooden propeller costs normally over $100.00. A four-bladed metal propeller cost approximately $800.00. While the cost of injection molding four-bladed propellers with shaft extension can be manufactured at a cost below $50.00.
U.S. Pat. No 3,670,382 to Keehan, U.S. Pat. No. 3,423,700 to Hardy, U.S. Pat. No. 2,659,444 to Stanley, U.S. Pat. No. 3,470,604 to Zenick, U.S. Pat. No. 3,438,116 to Stengle, Jr., U.S. Pat. No. 2,679,913 to Scott, U.S. Pat. No. 2,058,618 to Patzig, U.S. Pat. No. 1,388,657 to McDonald et al and U.S. Pat. No. 3,480,373 to Talbot all disclose different types of blade design, propeller design and methods of securing articles of manufacture through the use of thermoplastic. None of the above patents disclose the unique features of the injection molded propeller and method of making this molded propeller for producing a positive lock propeller mounted on a drive shaft.